The present invention relates to compressed fluid systems for vehicles. It finds particular application in conjunction with systems utilizing a pair of air dryers for removing moisture from compressed air and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.
Transit coaches and air-assisted bulk-off load units are illustrative of compressed air systems used for operating brakes and accessories (e.g., tire inflation systems) of vehicles (e.g., heavy-duty trucks, tractors, trailers, or tractor-trailer combinations). Known air dryers cannot meet the demands of these systems. More specifically, a desiccant material in the air dryer becomes overwhelmed and saturated, ultimately resulting in loss of function.
Continuous flow air dryers are used for air brake vehicle applications where high air use calls for extended charging times and high compressor duty cycles. Continuous flow systems, therefore, typically use a pair of air dryers between a source of compressed air and a storage reservoir. By occasionally purging air to exhaust from an air dryer, the dryer (specifically, the desiccant material) is regenerated and is more effective in removing moisture during its next duty cycle. Accordingly, switching arrangements that alternate the pair of air dryers between charging the reservoir and purging (e.g., one air dryer is regenerated while the other air dryer supplies dry air to the reservoir) have been developed.
Recently, additional onboard features such as bulk unload and central tire inflation systems have become more common. These systems increase the demand for compressed air. To meet the increased demand, some vehicle manufacturers have started providing high output compressors to ensure adequate air supply. One popular high output compressor used on commercial highway vehicles includes a turbo-charge inlet for receiving pressurized air from the engine air intake manifold. Under full boost conditions, this compressor can produce 70 SCFM or more. This output is more than most commercial air dryers can handle without causing excessive pressure at the outlet of the compressor. Thus, two dryers are typically plumbed in parallel to keep the head pressure within acceptable limits. However, when used in parallel, the air dryers cannot provide continuous air because they will need to be taken offline together to be purged. Accordingly, two pairs of air dryers would need to be used to accommodate the high output compressor and still provide continuous run functionality. This adds complexity and cost to the system, and requires additional onboard space for the extra components.
The present disclosure sets forth a new and improved apparatus, system and method which address the above-referenced deficiencies of the art.